Natural products have made enormous contributions to human health. The search for new lead compounds from natural sources continues to be a crucial element in modern anticancer drug discovery. Our long-term goal is to discover anticancer drugs that act by novel mechanisms from plant- and lichen-associated fungi of the Sonoran desert, thereby providing further support for our hypothesis that organisms living in association with one another in this unique environment elaborate a relatively unexplored repertoire of potent bioactive compounds with which to mediate their interactions and enhance their survival. The specific aims of this interdisciplinary and inter-institutional project are to: 1. expand our unique bio-resource of Sonoran desert plant- and lichen-associated fungi and optimize biosynthetic potential of 500 selected fungal strains and prepare 2,500 extracts for evaluation; 2. screen extracts for anticancer activity using cell-based biological and molecular approaches including: (a) an assay established during our previous grant period and recently modified to detect compounds capable of heat shock induction and inhibition of heat shock induction, followed by assays for direct interaction with Hsp90 including luciferase-refolding and binding assays for compounds isolated using the heat shock induction assay; (c) an assay for inhibitors of cell motility at sub-cytotoxic concentrations, and (d) a conventional dye reduction assay for inhibition of proliferation/survival based on five sentinel cancer cell lines to avoid the discovery of general cytotoxic agents; 3. dereplicate active extracts, culture on large-scale up to five promising fungal strains per year and subject their extracts to bioassay-guided fractionation to isolate and characterize bioactive compounds; and 4. define molecular mechanisms of action using genomic and proteomic approaches for the most promising compounds based on their activity, structural novelty, and potency. We expect that the most interesting compounds will serve as leads for further optimization in the development of novel anticancer agents with unique mechanisms of action. At a more basic scientific level, however, the innovative chemical biology approach we propose should help define the mechanisms by which (a) chaperones such as Hsp90 facilitate oncogenesis, and (b) small-molecules inhibit cancer cell migration involved in invasion and metastasis, leading to enhancement of our overall ability to prevent and cure cancers, and therefore have a great impact on public health.